Tuesday, June 17, 2025
12:00 PM - 01:00 PM
SED Director’s Seminar
Please join us for the SED Director’s Seminar hosted by the Exoplanets and Stellar Astrophysics Laboratory, Code 667!
Speaker: Ken Carpenter/667
Topic:The Hubble Space Telescope at 35: Highlights and Future Focus
Speaker: Dana R. Louie/Catholic University Title: JWST-TST DREAMS: A Precise Water Abundance for Hot Jupiter WASP-17b from the NIRISS SOSS Transmission Spectrum
Speaker: Keighley Rockcliffe/UMBC
Topic: Exoplanet characterization: atmospheric escape
Read more about this event Speaker: Ken Carpenter/667
Topic:The Hubble Space Telescope at 35: Highlights and Future Focus
Speaker: Dana R. Louie/Catholic University Title: JWST-TST DREAMS: A Precise Water Abundance for Hot Jupiter WASP-17b from the NIRISS SOSS Transmission Spectrum
Speaker: Keighley Rockcliffe/UMBC
Topic: Exoplanet characterization: atmospheric escape
Tuesday, June 17, 2025
03:30 PM - 05:00 PM
ASD Colloquium
Little Red Dots and Insights into Early Black Hole Growth from JWST
Dale Kocevski (Colby College)
One of the more surprising results from JWST has been the discovery of a large population of broad-line AGN at z > 5 that are 2-3 dex fainter that bright quasars identified from the ground. These sources are powered by black holes (BHs) with masses of order 10^7 Msol, making them the least-massive BHs known in the early universe. Studies in this low-mass regime are key to constraining models of BH seeding and the early growth history of SMBHs. I will discuss recent AGN-related results from the CEERS survey and what they tell us about galaxy-BH co-evolution out to the epoch of reionization. This includes the discovery of an actively accreting SMBH at z=9.3, as well as our work constraining the BH-galaxy mass relationship in the lowest mass range yet probed in the early universe. Finally, I will discuss the discovery of a large population of obscured AGN candidates at z>5 known as Little Red Dots (LRDs). While the nature of these sources is still heavily debated, we find that roughly 80% exhibit broad emission lines in their spectra and our X-ray spectral analysis confirms that they are moderately obscured, with column densities of log (nH/cm^-2) > 23. In addition, we find a quarter of LRDs exhibit narrow blue-shifted Balmer absorption features in their spectra, suggesting an outflow of high-density, low ionization gas that may also help obscure these sources. I’ll discuss the properties of these enigmatic sources and the current evidence for and against their AGN nature.
Read more about this event Dale Kocevski (Colby College)
One of the more surprising results from JWST has been the discovery of a large population of broad-line AGN at z > 5 that are 2-3 dex fainter that bright quasars identified from the ground. These sources are powered by black holes (BHs) with masses of order 10^7 Msol, making them the least-massive BHs known in the early universe. Studies in this low-mass regime are key to constraining models of BH seeding and the early growth history of SMBHs. I will discuss recent AGN-related results from the CEERS survey and what they tell us about galaxy-BH co-evolution out to the epoch of reionization. This includes the discovery of an actively accreting SMBH at z=9.3, as well as our work constraining the BH-galaxy mass relationship in the lowest mass range yet probed in the early universe. Finally, I will discuss the discovery of a large population of obscured AGN candidates at z>5 known as Little Red Dots (LRDs). While the nature of these sources is still heavily debated, we find that roughly 80% exhibit broad emission lines in their spectra and our X-ray spectral analysis confirms that they are moderately obscured, with column densities of log (nH/cm^-2) > 23. In addition, we find a quarter of LRDs exhibit narrow blue-shifted Balmer absorption features in their spectra, suggesting an outflow of high-density, low ionization gas that may also help obscure these sources. I’ll discuss the properties of these enigmatic sources and the current evidence for and against their AGN nature.
Monday, June 23, 2025
02:00 PM - 03:00 PM
Astrochemistry Seminar
JOYS+ study of solid state 12C/13C isotope ratios in protostellar envelopes with JWST
Nashanty Brunken (Graduate Student, University of Leiden)
CO2 and CO ice have proven to be invaluable when studying the chemical evolution of interstellar material. Both species have multiple vibrational modes in the near- and mid-infrared, and the ice absorption bands of CO2 ice are highly sensitive to their local chemical environment making CO2 ice an ideal tracer of physicochemical processes.
Additionally, observations of CO2 and CO ice provide a unique opportunity to quantify the solid state 12C/13C ratio in protostellar envelopes and compare the findings with carbon isotope ratios measured in molecular clouds, disks, comets and most recently exoplanet atmospheres. Studies of carbon isotope ratios are crucial for our understanding of fractionation processes in astronomical environments. Now with the new era of the James Webb Space Telescope the entire 2 - 28 μm spectral region has become available at high S/N, enabling for the first time a simultaneous detection of the various weak and strong ice absorption features of CO2, CO and their isotopologues in solar-mass and high mass protostars. In the JOYS+ study we quantify the solid state 12C/13C ratios in a large sample of 17 low-mass young stellar objects using NIRSpec and MIRI observations of CO2 and CO ice. Additionally, we combine the observations from the IPA program and JOYS+ program with high resolution laboratory spectra to analyze the band profiles of the 2.70 μm and the 15.2 μm bands of 12CO2 and the 4.39 μm band of 13CO2 of several low and and high mass protostars.
Read more about this event Nashanty Brunken (Graduate Student, University of Leiden)
CO2 and CO ice have proven to be invaluable when studying the chemical evolution of interstellar material. Both species have multiple vibrational modes in the near- and mid-infrared, and the ice absorption bands of CO2 ice are highly sensitive to their local chemical environment making CO2 ice an ideal tracer of physicochemical processes.
Additionally, observations of CO2 and CO ice provide a unique opportunity to quantify the solid state 12C/13C ratio in protostellar envelopes and compare the findings with carbon isotope ratios measured in molecular clouds, disks, comets and most recently exoplanet atmospheres. Studies of carbon isotope ratios are crucial for our understanding of fractionation processes in astronomical environments. Now with the new era of the James Webb Space Telescope the entire 2 - 28 μm spectral region has become available at high S/N, enabling for the first time a simultaneous detection of the various weak and strong ice absorption features of CO2, CO and their isotopologues in solar-mass and high mass protostars. In the JOYS+ study we quantify the solid state 12C/13C ratios in a large sample of 17 low-mass young stellar objects using NIRSpec and MIRI observations of CO2 and CO ice. Additionally, we combine the observations from the IPA program and JOYS+ program with high resolution laboratory spectra to analyze the band profiles of the 2.70 μm and the 15.2 μm bands of 12CO2 and the 4.39 μm band of 13CO2 of several low and and high mass protostars.